Priscilla Presley dated many famous men after divorcing Elvis, but she kept her relationship with Robert Kardashian to herself.

In her new memoir “Softly, As I Leave You: Life After Elvis” (Grand Central Publishing, 320 pp., on sale Tuesday, Sept. 23), she recalls leaping out of bed with Kardashian, who was sound asleep, to take a call from the King of Rock ‘n’ Roll at 2 in the morning.

Elvis would “have gone ballistic, maybe literally, if he’d known Robert was in my bedroom," she writes in an early copy of the book provided to USA TODAY. “Elvis always carried a loaded gun, sometimes more than one.”

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It never occurred to him that Priscilla might have been asleep. And “it had certainly never occurred to him that I might be with another man.” She recalls Elvis brimming with enthusiasm as he described a great show that night (“Damn, I was knocking ‘em out!”).